Methods of Manufacturing a Communication Cable

ABSTRACT

Cable foil tape having random or pseudo-random patterns or long pattern lengths of discontinuous metallic shapes and a method for manufacturing such patterned foil tape are provided. In some embodiments, a laser ablation system is used to selectively remove regions or paths in a metallic layer of a foil tape to produce random distributions of randomized shapes, or pseudo-random patterns or long pattern lengths of discontinuous shapes in the metal layer. In some embodiments, the foil tape is double-sided, having a metallic layer on each side of the foil tape, and the laser ablation system is capable of ablating nonconductive pathways into the metallic layer on both sides of the foil tape.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/715,051, filed Mar. 1, 2010, which claims priority to U.S.Provisional Application No. 61/157,067, filed Mar. 3, 2009, the subjectmatter of which is hereby incorporated by reference in its entirety

INCORPORATION BY REFERENCE

The present application incorporates by reference in their entiretiesthe following U.S. Provisional Patent Applications:

1. Ser. No. 61/034,312, filed Mar. 6, 2008 and entitled, “CommunicationCable with Improved Crosstalk Attenuation.”

2. Ser. No. 61/054,330, filed May 19, 2008 and entitled, “CommunicationCable with Improved Crosstalk Attenuation.”

3. Ser. No. 61/112,794, filed Nov. 10, 2008 and entitled “CommunicationCable with Improved Crosstalk Attenuation.”

FIELD OF THE INVENTION

The present invention is generally directed to communication cables andmore specifically directed to mosaic tape having fixed, random and/orpseudo-random pattern lengths for use in communication cables, andmanufacturing methods for producing mosaic tapes.

BACKGROUND OF THE INVENTION

In the development of 10 Gigabit per second (Gbps) network cable (forexample, Category 6A cable), the alien crosstalk specificationparameters (as defined in the ANSI/TIA/EIA-568-C.3 specification) havebeen challenging specification parameters to satisfy. Through the use ofa mosaic tape (i.e., a plastic tape having discontinuous metallic shapeson one or both sides of the plastic tape), alien crosstalk can bereduced such that the alien crosstalk specification parameter can bemet. However, due to tool-set limitations of current mosaic tapemanufacturing processes, such as die-cutting, only fixed-shaped-metallicpatterns or variable-metallic patterns that have relatively short-periodlengths can be fabricated. Further, when manufactured using conventionalprocesses, gaps between metallic shapes of the mosaic tape are widerthan what is generally desired in order to adequately reduce aliencrosstalk. Also, the costs associated with conventional manufacturing ofmosaic tape tend to be relatively expensive.

There is a need in the art for a method and apparatus to improve thereduction in alien crosstalk and to improve the frequency response ofcables having one or more twisted-pair signal wires.

SUMMARY OF THE INVENTION

According to some embodiments, the present invention provides improvedreduction of alien crosstalk by forming fixed metallic patternsaccording to a design or pattern of metallic shapes or strips (primarilywith respect to the longitudinal length of the pattern) such thatundesirable electromagnetic couplings are not generated between themosaic tape and the twisted wire pairs that the mosaic tape is wrappedaround. An undesirable coupling is shown in graph 101 of FIG. 1A. FIG.1A shows a coupling peak 106 in the power sum alien near end crosstalk(PSANEXT) performance spectrum 107 of a communication link, which iscaused by the interaction of a prior art mosaic tape with the twistedwire pairs. The tested link fails to satisfy the alien crosstalkspecification upper limit 105, (the PSANEXT specification under theCategory 6a of ANSI/TIA/EIA-568-C.3 Cabling Standard). Mosaic tapeshaving metallic shapes with periodic pattern lengths according to thepresent invention are designed such that the pair lay lengths of each ofthe wire pairs are taken into account in order to prevent such unwantedcouplings in the alien crosstalk performance spectrum from occurring.These limitations can act to restrict the selection of mosaic patternlengths, as well as to restrict the tolerances of the mosaic tape and/orlimit the range and tolerance of pair lay lengths of the twisted pairswithin the cable.

One technique for reducing the magnitude of the potential couplingbetween the mosaic tape and the twisted pairs is to fabricate anon-fixed length and/or a non-fixed shape pattern within the mosaictape, such as a random pattern or a pseudo-random pattern that appearsrandom and/or non-coupling at the frequencies of interest. Frequenciesof interest include, but are not limited to frequencies of cablingapplications such as Cat 5e (up to 100 MHz); Cat 6 (up to 250 MHz); Cat6a (up to 500 MHz); cable used in 40G Base-CR4 (up to 10 GHz); and cableused in 100G Base-CR10 (up to 10 GHz). These frequencies havewavelengths, λ, in the range of a few centimeters to a many meters. Toavoid couplings due to a short repeated pattern (wherein the repeatedpattern or portions of the pattern are of a length that generates acoupling), if the mosaic pattern is to be repeated, the repeated patternshould be as long as possible. For example, in one embodiment thepattern should be longer than the wavelength of the couplingfrequencies. In some embodiments of the present invention, repeatedpattern lengths greater than approximately five meters (5 m) are used.However, if the mosaic elements are too long they can createelectromagnetic compatibility problems, the worst case being aconductive element which is as long as its respective cable, in whichcase it acts like an un-terminated shield. The present invention fills aneed in the art for a method and apparatus for better reduction of aliencrosstalk and higher frequency capabilities, by fabricating mosaic tapewith narrow gap spacing between metallic portions and with random orpseudo-random patterns having a long repeat length, or even norepetition of the pattern for the length of the cable. The narrow gapbetween metallic shapes is advantageous for several reasons. The use ofnarrow gaps allows for the use of a single-sided mosaic tape whichlowers the cost of the tape and makes the tape thickness much thinner,resulting in an overall smaller cable diameter. Narrower gaps betweenmetallic shapes also improve alien crosstalk performance. A laserablation system, as described below, may be used in a method by whichrandom or pseudo-random patterns of metallic shapes are fabricated. Themethod provides high flexibility of pattern shapes and repeat lengths.

In some embodiments, the present invention provides a cable havingreduced alien crosstalk and an apparatus, method, and system formanufacturing the cable with reduced alien crosstalk. The cable withreduced crosstalk may include a plurality of twisted pairs of insulatedconductors, a laminate film having a fixed, random, and/or pseudo-randomlength patterned metallic layer wrapped around the plurality of twistedpairs, and an insulating cable jacket that has a central longitudinalaxis that encloses the twisted pairs of insulated conductors, whereinthe metallic layer on the mosaic tape provides electrical and magneticattenuation between wire-pairs within the cable and wire-pairs within asecond cable, thereby reducing alien crosstalk. In addition, improvedplacement and widths of gaps within the metallic layer can reducecouplings between the twisted wire pairs and the laminate film.

The present invention provides for an office, school, hospital,government facility, transportation vehicle, and residential ormanufacturing buildings with an installed cable “plant” of high-speed(e.g., up to 10 Gbps or more) interconnection cables, wherein the cableplant is or can be part of an integrated network of computer servers andclients. One example of such an interconnection cable 150 is shown inFIG. 1B.

In some embodiments, an apparatus according to the present inventioncomprises a film payoff mechanism (described further below) configuredto payoff a film, at least one laser configured to emit laser light thatimpinges on the film and ablates away a portion of the film to generategaps in a metallic layer of the film, and a film take up mechanismconfigured to take up the film after the film has passed through theablation step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a graph showing an alien crosstalk performance spectrumhaving a coupling peak caused by the interaction of a prior art mosaicmetallic tape with one or more of the twisted wire pairs.

FIG. 1B is an example of an interconnection cable according to someembodiment of the present invention.

FIG. 2A is a cross-sectional diagram of cable tape according to someembodiments of the present invention taken along section line 2A-2A inFIG. 4A.

FIG. 2B is a cross-sectional diagram of cable tape according to someembodiments of the present invention.

FIG. 2C is a cross-sectional diagram of cable tape according to someembodiments of the present invention.

FIG. 2D is a cross-sectional diagram of cable tape according to someembodiments of the present invention.

FIG. 3A is a schematic diagram of a laser ablation system according tosome embodiments of the present invention.

FIG. 3B is a schematic diagram of a laser ablation system according tosome embodiments of the present invention.

FIG. 3C is a perspective diagram of a laser ablation system according tosome embodiments of the present invention.

FIG. 3D is a perspective diagram of a laser ablation system according tosome embodiments of the present invention.

FIG. 4A is a top view of a fixed mosaic pattern according to someembodiments of the present invention.

FIG. 4B is a top view of a random or pseudo-random mosaic tape accordingto some embodiments of the present invention.

FIG. 4C is a top view of another random or pseudo-random mosaic tapeaccording to some embodiments of the present invention.

FIG. 4D is a top view of another random or pseudo-random mosaic tapeaccording to some embodiments of the present invention.

FIG. 5 is a graph showing keep-out areas of effective pair lay lengthsfor preventing electromagnetic coupling when a mosaic tape is used witha fixed length (L) of metallic shapes according to some embodiments ofthe present invention.

FIG. 6 is a partially exploded, fragmentary view of an embodiment of acable with a mosaic tape according to the present invention.

The examples set out herein illustrate preferred embodiments of theinvention, and such examples are not to be construed as limiting thescope of the invention in any manner.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. Other embodiments may be utilizedwithout departing from the scope of the present invention.

Further, it is to be understood that the drawings do not necessarilyillustrate gaps in the metallic layers of tapes according to the presentinvention to scale. For illustration purposes, the gaps between metallicportions of the metallic layer have been illustrated wider than scaleillustrations would indicate.

FIG. 2A is a cross-sectional diagram of film 201 along the line segment2A-2A shown in FIG. 4A, according to some embodiments of the presentinvention. Film 201 includes substrate 261, bond layer 262 and metalliclayer 263, wherein the bond layer 262 is used to connect the metalliclayer 263 to the substrate 261. Substrate 261 is a flexible lowdielectric-constant material polymer (e.g., ethylene copolymer) with athickness of around 25 micrometers. In some embodiments, the thicknessof the substrate 261 is between 5 micrometers and 500 micrometers orranges within that range. Metallic layer 263 is a highly conductivemetal (e.g., aluminum, gold, silver, copper or the like) and has athickness of around 10 micrometers. In some embodiments, the thicknessof the metallic layer 263 is between 0.1 micrometers and 100 micrometersor ranges within that range. Bond layer 262 may be a non-conductiveglue, and further, bond layer 262 may be a non-conductive glue with acolor pigment added to the glue in order to more readily absorb aparticular wavelength of laser light. When the laser light beam isincident onto the metallic layer 263 of film 201, the illuminatedmetallic section 422 absorbs the incident energy and ablates themetallic material. In this manner the isolated metallic shapes 421 areproduced. During this process, the illuminated material 270 in the bondlayer 262, can also be ablated.

FIG. 2B is a cross-sectional diagram of film 202 according to someembodiments of the present invention. Film 202 is similar to film 201 asdescribed above, except that film 202 includes an absorbing layer 264 ontop of the metallic layer 263 that is used to more readily absorb aparticular wavelength of laser light or to reduce the reflection oflaser light incident on metallic layer 263.

FIG. 2C is a cross-sectional diagram of film 203 according to someembodiments of the present invention. Film 203 is similar to film 201 asdescribed above, except that film 203 includes a second metal layer 265and a second bond layer 266, wherein bond layer 266 is used to connectmetallic layer 265 with the substrate 261. Metallic layer 265 is ahighly conductive metal (e.g., aluminum, gold, silver, copper or thelike) and has a thickness of around 10 micrometers. In some embodiments,the thickness of the metallic layer 265 is between 0.1 micrometers and100 micrometers or ranges within that range. In some embodiments, bondlayer 266 is a non-conductive glue. In some other embodiments, bondlayer 266 is a non-conductive glue with a color pigment added to theglue in order to more readily absorb a particular wavelength of laserlight. In some embodiments, metallic layer 263 and metallic layer 265are formed from the same metal and have the same thickness. In someother embodiments, metallic layer 263 and metallic layer 265 are formedfrom different metals and can have different thicknesses.

FIG. 2D is a cross-sectional diagram of film 204 according to someembodiments of the present invention. Film 204 is similar to film 203 asdescribed above, except that film 204 includes absorbing layer 264 ontop of metallic layer 263 and a second absorbing layer 267 on top ofmetallic layer 265.

FIG. 3A is a schematic diagram of a laser ablation system 301 forfabricating fixed, random and/or pseudo-random patterns on a metalliccable tape according to some embodiments of the present invention. Laserablation system 301 includes a film payoff mechanism to payoff a film313 wherein film 313 is contained on a cylindrical (or similar) payoffspool 310, drive rollers and encoders 314 to move film 313, one or morelasers 311 used to pattern film 313, and a film take up mechanism totake up film 313 onto a cylindrical take up spool 312 after film 313 hasbeen patterned. The one or more lasers 311 may be contained within anenclosure 315 to prevent operators from being injured by the laserlight, and film 313 passes through enclosure 315 where film 313 ispatterned by the one or more lasers 311. The film 313 enters enclosure315 on a first side and exits enclosure 315 on a second and oppositeside. Accordingly, all the components may be contained within enclosure315. That is, the film payoff mechanism 310, film 313 contained on acylindrical payoff spool, the drive rollers and encoders 314, the one ormore lasers 311 used to pattern film 313, and the film take up mechanism312 used to take up film 313 onto a cylindrical take up spool after film313 has undergone an ablation process may all be contained within theenclosure 315.

The one or more lasers 311, may be semiconductor (diode or otherwise)lasers, fiber lasers, pulsed-fiber lasers, gas lasers, solid statelasers, liquid lasers, chemical lasers or the like, and emit a laserlight having a wavelength of, preferably, around 1064 nm. In someembodiments, the wavelength of the laser light emitted by the one ormore lasers 311 is in the range of 100 nm to 1800 nm.

The one or more lasers 311 are used to ablate a conductive layer (e.g.,aluminum, gold, silver, copper or the like and alloys thereof) from asubstrate (e.g., polymer). The one or more lasers may require the use ofbeam guidance or delivery technology such as lenses, mirrors,beamsplitters, motors, light pipes, fiber optics and the like (none ofwhich are shown in FIG. 3A). The one or more lasers 311 preferably havea wavelength that is selected such that the laser light penetratesthrough the polymer substrate leaving the polymer substrate unharmed.The laser light produced by the one or more lasers 311 may be absorbedby a bond layer (e.g., a non-reflective glue layer used to connect thepolymer substrate and the metallic layer or a glue layer that has acolor pigment added in order to more readily absorb a particularwavelength of laser light and is used to connect the polymer substrateand the metallic layer) to heat up the metallic layer. This heatselectively vaporizes the metallic layer and possibly the bond layerthereby creating a non-conductive path through the metallic layer. Thisforms an arrangement of metallic shapes separated from one another bynon-conductive gaps in a mosaic-type arrangement, and the resulting tapemay be called a “mosaic tape.”

Alternatively, the laser light produced by the one or more lasers 311impinges directly on the metallic layer, without first traveling throughthe substrate or the bond layer, and selectively ablates the metalliclayer down to the bond layer or the substrate, thereby creating anon-conductive path in the metallic layer. The metallic layer may becoated with an absorbing layer used to enhance the absorption of thelaser light impinging on the metallic layer to improve the ablationefficiency.

The laser ablation system 301 can be installed at many locations on amanufacturing line (e.g., as a stand alone system as shown in FIG. 3A or3B, as part of a web slitting system, on-line at a cabler (twinner,strander, and/or extrusion/jacketing), or as part of other cablemanufacturing processes).

Some advantages of using laser ablation system 301 for the manufactureof mosaic tape are as follows:

1. The use of laser ablation provides a very small gap between metallicshapes (this improves performance) which is not possible with mechanicalsystems such as die cutting. According to some embodiments of thepresent invention, gaps of from about 0.5 mil to about 8 mil in widthare created between the conductive shapes, in combination withconductive shape lengths of from 0.75 inch to 2.5 inches;

2. Provides an easily changeable pattern or randomization length for themetallic shapes (which can be flexibly modified to be short, long, orinfinite); and

3. Provides the ability to implement a wide variety of geometric shapesfor the metallic shapes, from regular and irregular polygons to simpleand complex curved shapes and combinations thereof (to improveperformance).

FIG. 3B is a diagram of a laser ablation system 302 according to someembodiments of the present invention. Laser ablation system 302 issimilar to laser ablation system 301 as described above, except that theone or more lasers 311 or beams of laser ablation system 302 can belocated on either side of the film 313, thereby allowing laser light toimpinge on both surfaces of the film 313.

In some embodiments, film 313 is preferably similar to film 201 or film202 as shown in FIG. 2A and FIG. 2B, respectively, and described above.In these embodiments, laser light from one or more lasers located abovethe top surface of film 313 and one or more lasers located below thebottom surface of film 313 illuminates both surfaces of film 313individually or substantially simultaneously. For example, if the film313 is oriented such that the metallic layer is the top surface and thesubstrate is the bottom surface, the laser light from the beam or beamslocated above the top surface directly impinges on the metallic layer(or the absorbing layer as described in FIG. 2B) to selectively ablateaway the metal. The laser light from the lasers located below the bottomsurface has a wavelength such that the laser light passes through thesubstrate and is absorbed by the bond layer to selectively heat up andvaporize the metallic layer. The wavelength of light produced by the oneor more lasers located above the top surface of film 313 and thewavelength of light produced by the one or more lasers located below thebottom surface of film 313 may be different. The wavelength of lightproduced by the one or more lasers located above the top surface of film313 and the wavelength of light produced by the one or more laserslocated below the bottom surface of film 313 may be substantially thesame.

In some other embodiments, film 313 is preferably similar to film 203 orfilm 204 as shown in FIG. 2C and FIG. 2D, respectively, and describedabove. In these embodiments, laser light from one or more lasers locatedabove the top surface of film 313 impinges directly on the top surfacemetallic layer to selectively ablate away the top surface metallic layerand laser light from one or more lasers located below the bottom surfaceof film 313 impinges directly on the bottom surface metallic layer toselectively ablate away the bottom surface metallic layer.

FIG. 3C is a diagram of a laser ablation system 303 according to someembodiments of the present invention. Laser ablation system 303 issimilar to laser ablation system 301 as described above except thatlaser ablation system 303 includes multiple cylindrical payoff spools310 and multiple cylindrical take up spools 312 in order to loadmultiple spools of film, thereby allowing for the ablation process to beapplied to multiple films 313 simultaneously. Single laser 311 emitslaser light 316 to ablate the multiple films 313 and may be located on amoveable stage that allows the single laser 311 to move in multipledirections, thereby allowing the laser light 316 from single laser 311to selectively ablate the metallic layer from the multiple films 313. Amechanically or electrically controlled minor can also be used toreflect the laser light from the single laser 311 to selectively ablatethe metallic layer from the multiple films 313. Multiple lasers 311 canbe utilized in a similar manner.

FIG. 3D is a diagram of a laser ablation system 304 according to someembodiments of the present invention. Laser ablation system 304 issimilar to laser ablation system 301 as described above except thatlaser ablation system 304 includes a cylindrical payoff spool 310capable of accepting spools of film having a width that is greater thanat least twice the width of a single cable wrap film to payoff singlefilm 313. Cutting mechanisms (which may include laser cutting tools) areused to divide the single film 313 into multiple films 317, each film317 having a width appropriate for use as a cable wrap, and multiplecylindrical take up spools to take up the multiple films 317 after thefilms 317 have been patterned. Single laser 311 emits laser light 316 toablate the multiple films 313 and may be located on a moveable stagethat allows the single laser 311 to move in multiple directions, therebyallowing the laser light 316 from single laser 311 to selectively ablatethe metallic layer from the multiple films 313. A mechanically orelectrically controlled minor can also be used to reflect the laserlight from the single laser 311 to selectively ablate the metallic layerfrom the multiple films 313.

Laser based ablation systems 301, 302, 303, and 304 are used to producea fixed pattern, a random collection of shapes, and/or a pseudo-randompattern of mosaic tape capable of being used as a cable tape. The randomor pseudo-random pattern lengths of discontinuous metallic shapes reduceor substantially eliminate the interaction between the mosaic tape andthe internal twisted pairs. The fixed, random and/or pseudo-randompattern lengths of discontinuous metallic shapes may be alternativelymanufactured with the use of a mechanical (e.g., selective controlledmilling) or an electrical based (e.g., selective controlled arcing)ablation systems to produce a random effect or a long period patternlength of mosaic tape.

The use of fixed, random and/or pseudo-random patterns of discontinuousmetallic shapes substantially reduces the magnetic and electric fieldcoupling between neighboring cables and more specifically preventsunwanted coupling between the twisted pairs within the cable and themosaic tape which would result in a high coupling between neighboringcables. In some embodiments, a pseudo-random pattern could have a periodof about 5.0 m or in a range between 0.1 m and 100 m.

FIGS. 4A, 4B, 4C, and 4D are diagrams showing different possible mosaicpatterns 401, 402, 403, and 404, respectively, that a laser ablationsystem according to some embodiments of the present invention canproduce. In FIG. 4A, a fixed pattern 401 is shown wherein the metallicshapes 421 are shown in gray and the white regions or gaps 422 representareas wherein the metallic layer has been ablated away. In FIGS. 4B and4C, random patterns (402 and 403) are shown. In FIG. 4D a randomdistribution of randomized shapes 404 having non-linear (i.e., curved)ablated regions or paths is shown. The pattern ablated into the metalliclayer of the film or tape is preferably chosen to reduce aliencrosstalk. This film or tape can then be wrapped around the twisted-wirepairs within a cable such that the film or tape can cover the internalpairs once or multiple times in order to improve the couplingattenuation, thereby reducing the alien crosstalk that would result frominteractions with nearby cables.

For fixed-length metallic patterns of the mosaic tape, the effectivewire-pair twist lay (1/[{1/pair lay}+{1/strand lay}] must be designed soas not to create undesired electromagnetic coupling between the tape andwire-pair. Undesired electromagnetic coupling occurs to a greater extentwhen integer or ½ integer numbers of wire-pair twist periods aredirectly below a metallic shape. If this condition occurs over a numberof successive metallic shapes, a periodic signal is imparted onto thesuccessive metallic shapes which couples efficiently to neighboringcables (particularly to cables of similar construction). The frequencyof this interaction between the tape and the wire-pair is associatedwith how close the effective wire-pair twist period is to the integer or½ integer related mosaic length. For example, if the wire-pair twistperiod is exactly equal to the metallic shape length the frequency islow. As the wire-pair twist period gets slightly larger or smaller thanthe mosaic shape length the frequency increases.

The most sensitive frequencies are the ones that lie in the frequencyrange that the application requires (e.g., 10G Base-T requires afrequency range between 1 MHz and 500 MHz). Hence it is preferable forthere to be no undesired couplings in the frequency range of interest.Therefore, a region of lengths about the integer or ½ integer relatedmosaic length define the frequency range that must be avoided for aparticular application (e.g., 10G Ethernet). These regions of lengthsdefine “keep-out” zones for the effective wire-pair twist period. Hencefixed-length mosaic patterns can be designed in this way to preventunwanted electromagnetic coupling from occurring in the frequency rangeof interest. A completely random shape distribution and/or pseudo randompattern can be employed which substantially eliminates the unwantedcoupling from occurring.

FIG. 5 shows a graph 501 of keep-out areas (to obtain effective pair laylengths) when a mosaic tape is used with metallic shapes having a fixedlength period L, where L is the length of the metallic shape plus thewidth of the gap between adjacent metallic shapes. Note that for FIG. 5,L=1.0 inches, but the graph can be scaled for other values of L.Avoiding the keep-out areas prevents or reduces unwanted electromagneticcoupling from occurring in the alien crosstalk frequency spectrum ofinterest. Specifically, FIG. 5 shows a graph 501 that demonstrates anexample of the relationship between the fixed pattern length (L) of themetallic shapes in the mosaic tape and the effective pair lay length(which is equal to the pair lay length combined with the strand laylength) within a cable. The relationship is shown or described, as“keep-out” zones (i.e., the gray boxes in the graph) where the effectivepair lay length of each of the wire pairs within the cable should notreside or where the length (L) of the fixed length metallic shapesshould be changed to accommodate the effective pair lay length set. Forexample, referring to FIG. 5, if the fixed length of the metallic shapesis L then keep-out zone 584 dictates that the effective pair lay lengthshould not be around 1.000 inch (i.e., it should be outside of thelength assigned by the grey box 584). An alternative way of utilizingFIG. 5 is as follows: for an effective pair lay length of 0.500 inch,keep-out zone 585 dictates that the fixed length of the metallic shapesshould not be L. The length L of the metallic shapes combined with thegaps must either be increased or decreased to shift the box 585 to theright or left of the pair lay length of 0.5 inch. Note that the higherorder terms of the integer components 582 (e.g. L/N where N is large) orthe half integer components 581 (e.g., NL/2 where N is large and odd) donot result in a strong interaction between the twisted wire-pair and themosaic metallic pattern due to the number of wire-pair twist periodsinteracting with one metallic shape. These higher order terms result ina much smaller contribution to alien crosstalk.

For a metallic shape length of L=1.0 inches, a strand lay of 4.0 inches,and four twisted pairs having pair lays of 0.5 inches (pair 1, effectivepair lay of 0.444 inches), 0.65 inches (pair 2, effective pair lay of0.559 inches), 0.74 inches (pair 3, effective pair lay of 0.6245inches), and 0.86 inches (pair 4, effective pair lay of 0.708 inches),it can be seen from FIG. 5 that all of the effective pair lays avoid thekeep out zones. As the low order keep-out zones 583-586 are missed, themosaic tape/strand lay/pair lays combination performs adequately.

Following fabrication of the mosaic tape according to the presentinvention, mosaic tape 696 can be integrated into a communication cableconstruction 601 as shown in FIG. 6. In FIG. 6 a barrier tape 693 iswrapped around the twisted pairs 695 and wire-pair separator 694. Themosaic tape 696 is wrapped over this assembly and the jacket 692surrounds the mosaic tape 696.

One of the advantages of the present invention is that a laser ablationmethod to produce the mosaic tape can create relatively thin gaps orvoids between conductive elements when compared to mechanical diecutting methods. A thin gap is preferred because it has improvedelectric field and magnetic field shielding characteristics.Consequently, mosaic tapes manufactured according to the presentinvention can have conductive elements on a single side of the tape, andsuch structure has the same performance, or nearly the same performance,as mosaic tapes manufactured with a die cutting method with conductiveelements on both sides of the tape. Additionally, the mosaic tapeaccording to the present invention can be manufactured at asubstantially lower cost compared to other tapes.

Another technique for reducing unwanted couplings is to randomize thetwist periods of the twisted wire-pairs within a cable. The resultingrandom relationships between a fixed (or random) pattern on the mosaictape reduces couplings and removes the dependency of the twistedwire-pairs' twist period to the periodicity of the mosaic's metallicshapes.

Alternatively, or additionally, a mosaic tape having a fixed periodicityof metallic shapes may be wrapped around a cable core having arandomized strand lay (sometimes called cable lay). In this fashion, thetwisted wire-pairs interact with the metallic shapes with a randomizedinteraction length, which reduces unwanted couplings.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationsmay be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

We claim:
 1. A method of manufacturing a communication cable including aplurality of twisted pairs of conductors stranded together to create acable core, the method comprising the steps of: establishing aneffective pair lay for each of the plurality of twisted pairs; choosingat least one length of corresponding metallic shapes for a laminatedfilm to prevent resonances with said effective pair lays; forming saidlaminated film having at least one layer of said metallic shapes, eachof said metallic shapes being approximately at least one said length;and wrapping said cable core with said laminated film.
 2. The method ofclaim 1, wherein said forming step includes the sub-step of laserablating gaps in said laminated film to create said metallic shapes. 3.The method of claim 2, wherein said gaps have a width ranging from about0.5 mil to about 8 mil.
 4. The method of claim 1, wherein said choosingstep includes choosing a single length for all of said metallic shapes.